Time element relays



Feb- 25 1964 s. B. AYLswoRTl-l 3,122,518

TIME mmm REIMS Filed Dec. l, 1959 4 Sheets-Sheet 1 10 67\66 79 60 6211 f2/7m( 16a m\\"\\\\v`\\ x\\|.\.\.\\\-\`\\ 6 70 @sa 7? 96 F J `74 956 97 146 926 m 75 gg?, .9a 775926 9,2 77 22h- 64 91 '92C 90 140 26 101 l \IZL 100 142 12 12C 165 136 1566 166 14 1746 164 102 157 74 165 166 2Q 1111 154m 1701i Fig 1.

1126 1776 126 116 11611 17C 150 l 1*. 4 124 m5 "115 I rml: "2 :yl 125 ...@l 114 |1126 112 161113 170 INVENTOR. 10a Selden AglszI/onh 106a BY 4. y n d- An-.

HIS A zgoRNL'Y Feb. 25, 1964 s..B. AYLswoRTl-l TIME imam- RELAYs sms @i INVENTOR Selden Ayl'woz'lz Sheets-Sheet 2 @uw v SSN m5 Filed Dec. 1. 1959 bm. Nw bw Nw Feb. 25, 1964 s. B. AYLswoRTH TIuE ELmENT RELAYs 4 Sheets-Sheet 5 fehlen B. AyLsa/orlflz Filed Dec. l, 1959 HIS A T TORNEY Feb. 25, 1964 s. B. AYLswoRTH 3,122,618

TIME Emmm- RELAYS Filed Dec. 1, 1959 4 Sheets-Sheet 4 INVENTOIL Selden Aglswonh BY dimi HIS ATTORNEY United States Patent O 3,122,618 TIME ELEMENT RELAYS Selden E. Aylsworth, Willrinshnrg, Pa., assigner to WestinghonseAir Bralre Company,`Wilmerding, Pa., a corporation of Pennsylvania Filed Dec. 1, 1959, Ser. No. 856,526 35 Claims. (Cl. Z00--105) My invention relates to timing relays, and more particularly to timing relays of the type comprising a contact which becomes closed at the expiration of a time interval of relatively long duration after the relay becomes energized.

in one form of timing relay, a clutch mechanism is employed comprising a brake wheel arranged to be held from rotating when the relay becomes energized. The brake wheel is acted upon, when thus immobilized, by a planetary gear assembly which is rotated in one direction through a predetermined distance corresponding to the desired timing cycle to nctuate an electrical contact and thereby complete the timing operation, and rotated freely in the opposite direction by its own weight, when the brake wheel is released, to its normal position to there await the start of another timing operation. ln relays of this type, it is essential that the brake wheel be rigidly locked against rotation during the timing operation so :as to prevent variations from the preselected operating time and thereby ensure preciseness of operation of the relay. An object, therefore, of my invention is to provide an improved clutch mechanism which, 'when used in connection with a timing relay, reliably performs the function of preventing rotation of the brake wheel for the period of time the relay is energized.

Another object of my invention is the provision, in a timing relay, of an electromagnetic clutch mechanism which is eiiicient in operation and more economical to manufacture than prior devices to thereby reduce the cost of such relays.

Still another object of my invention is to provide a timing relay including novel means for adjusting the duration of the timing cycle ofthe relay.

Yet another object of my invention is to provide a timing relay which includes means for locking the delicate parts of the relay from movement during shipment or handling, which means forms a constituent part of the relay and performs its holding function automatically the instantthe relay is detached or removed from its mounting base.

A still further object of my invention is to provide a novel and improved relay of the pendulum type.

Yet a further object of my invention is toprovide, in a relay of the pendulum type, novel and improved means for Idamping the pendulum.

Other objects and characteristic features of my invention will become apparent as the specilication proceeds.

ln accordance with my invention, and to attain the aforementioned objects, ll provide a self-timing relay including an operating coil, a stepping armature operable in response to the energization of the operating coil, an oscillating pendulum operatively connected with the armature and having self-contained means for damping it, and

contacts controlled by movement of the pendulum which, in turn, control the energization of the coil. A clutch magnet including a hollow core is provided to be energized at the initiation of the timing operation and comprises a iirst iixed pole piece projecting `from the core and a second pole piece concentric with the lirst pole piece and rotatable with respect thereto and arranged to be heldirnmobilized during the timing operation by a clutch armature normally biased apart from the pole pieces but movable into engagement therewith, in response to the energization of the clutch magnet, to thereby keep the second pole piece from rotating. A shaft, operatively connected with the stepping armature in such manner that the shaft is rotated in response to movement of the stepping armature, extends internally of the clutch magnet core and projects at both extremities well beyond the pole pieces. A planetary gear assembly, operatively connected ,with the shaft and with a gear krigid with the second pole piece, operates to close a timing contact after `a predetermined time interval following the energization of the clutch magnet.

l shall describe one form of relay embodying my invention, and shall then point out the novel features thereof in claims.

ln the accompanying drawings:

FIG. l is a side elevational lView, partially in section, of a relay in accordance with my invention.

FIG. 2 is a view showing in detail one form of holding .ieans embodying my invention as applied to the pendulum of the relay shown in FIG. 1.

FlG. 3 is a view taken on the line lll-lll of FIG. 2.

FIG. 4 is an isometric view showing one of the amplitude controlling weights adapted to be applied to the pendulum of the relay shown in FlG. l.

FIG. 5 is akfront elevational View of the relay shown in l.

FlG. 6 is y.a view, with certain of the parts removed, showing the time interval adjusting apparatus for the relay shown in FIGS. l and 5, as it appears when viewed from the right in FIG. 5,

FIG. 7 is a view of the time interval adjusting apparatus of the relay shown in FlGS. 1 and 5, substantially as is shown in FIG. 6, but with the 4apparatus adjusted to provide the minimum time interval available.

FIG. S is a View showing in more detail a member for damping the pendulum embodying my invention.

FIG. 9 is a view taken substantially on the line lX-IX of FlG. 5.

FlG. loris la view taken on the line X-X of FIG. 6.

FIG. 1l is a view, on a somewhat larger scale, with vcertain of the parts in section, showing principally the electror agnetic clutch assembly and drive shaft forming a part of the relay illustrated in FIGS. l and 5.

FlG. 12 is a view showing in isometric projection a section of the contact stack` structure and the support spring ,for supporting the operating ladder of the relay embodying my invention.

FIG. 13 is a yragmental View, in isometric projection, showing the gearing and, in greater detail, Lthe time interval adjusting apparatus' forming a part of the relay shown in FlGS. il and 5. j j

FlG. 14 is a schematic diagram of the electrical circuitry for the relay of FIGS. l yand 5. l

Similar reference characters refer to similar parts in each ,of the several views. j

Referring to the drawings, the relay, which is designated as a whole by the reference character 10, comprises a frame member i2 of suitable nonrnagneticmaterial, such as aluminum, having a vertical portion 12a and two horizontal forwardly extending portions 12b disposed on opposite sides of the relay. The portions 12b of frame member 12 are similar and each includes alongside the bottom thereof a transverse inwardly extending supporting rib 12C, which ribs are best seen in FIG. 5. A relatively thin mounting plate 14 of nonmagnetic material, which serves as a support for all of the operating parts of the relay, is disposed horizontally between the portions 12b of frame member 12 and is secured at each end to the upper side of the supporting ribs 12c'as by screws 16. The upper and lower portions 13a and 181i of a transparent cover 1S are attached to portions 12b of frame member l2 at the front of the relay by means of suitable screws, not shown. The relay l@ is adapted for plug-in application in a stationary mounting base 20 of the type well known in the art, and a pair of indexing pins 22 secured to the portion 12a of frame member l2 are provided in a well-known manner to align the relay with the mounting base 20 to prevent errors in replacement. When this relay is mounted in an operating position, that is, when it is plugged in, as illustrated in FIG. l, it will be understood that the rear side 24 of the portion 12a of frame member 12 will abut a forward side 20a of the mounting base in a manner to be practically fiush mounted thereagainst. It will also be understood in the following description that when the relay 10 is disposed in a nonoperating position, that is, when it is not mounted on the mounting base 2f?, the rear side 24 of the portion l2a of frame member 12 will ordinarily be completely separated from the forward side 20a of mounting base 2.0.

As best illustrated in FIG. 6, a contact block 26 of suitable insulating material, such as a phenol condensation product, extends rearwardly through an opening 28 in and adjacent to the upper end of portion 12a of frame member 12, and is secured to the portion 12a as by screws 30. A plurality of movable Contact fingers, here shown as three in number, and designated 32, 34 and 36 (FIG. are attached at one end to the top and underside of contact supports 38 of conductive material, which, in turn, extend rearwardly through the contact block and are rigidly affixed therein in any suitable manner herein not shown. Each of the contact supports terminates at the rear of the relay in a corresponding plug-in terminal, only two of which, herein designated 49, are shown in the drawings. A post 42 (FIG. 5) is attached to the underside of the contact block by means of screws 42a. Securely clamped between the lower end of post d2 and screws 42a is the offset portion 44a of a forwardly extending plate 44 provided with a back contact finger 45 which is riveted or otherwise secured to the upper side of plate 44, and at the lower side, with a supporting spring 48 similarly attached to the plate and arranged to uphold an operating ladder of molded insulating material indicated generally by the reference character 5t).

The operating ladder 5@ essentially comprises a relatively thin lower portion 50a, and a main body upper portion Stlb provided at both sides with transverse bosses 52 which cooperate in snug relationship with the free ends of the contact fingers 32, 34 and 36 in a well-known manner to move them simultaneously in response to movement of the operating ladder. Also provided on the operating ladder, and having generally U-shape when looking thereat in a downward direction, is a projection 54 formed with two relatively short and forwardly extending legs 54a. In assembled relation, as here illustrated, the free end of the supporting spring underlies and engages the projection 54, and is bent upwardly substantially normal to the longitudinal axis of the supporting spring to nest between legs 54a of projection 54. The bent portion of the supporting spring has a width slightly less than the Width of the major portion of the supporting spring and terminates in a pair of diametrically opposite fianges 56 which overlie the legs 54a on projection 54. The one side of the projection 54 opposite to the side thereof contiguous with the flanges 56 abuts upon the supporting spring at the point of reduction in width, and the projection is of a dimension to extend slightly below the underside of the supporting spring, as best seen in FIG. 6. Owing to the nested arrangement of the bent portion of the supporting spring, when the contact fingers occupy the positions shown connecting with the operating ladder, movement of the operating ladder relative to the supporting spring vertically, and horizontally in any plane, is limited to the play between the cooperating surfaces of projection 54 and the supporting spring. Preferably, the play between the surfaces of these parts is kept at a minimum to provide a firm connection therebetween and thus, the operating ladder can move neither forward nor backward. Moreover, under some conditions, say for contact adjusting reasons or for any other purpose, it is desirable to temporarily detach the operating ladder from the supporting spring. It should be noted particularly, therefore, that due to the manner in which the operating ladder is supported, removal thereof is easily accomplished merely by applying the sharp point of a suitable instrument or tool (not shown) to the fianges 56 on the supporting spring and moving the flanges outward sufiiciently until they no longer ride over the legs 54a on projection 54, whereupon the operating ladder may be lifted from the supporting spring and detached from the movable Contact lingers.

As will be explained more fully hereinafter, the operating ladder may at times be made to move upwardly from its normal position. When the operating ladder is thus moved, the contact fingers 32 and 34 will respectively engage the contact elements of a pair of front contact fingers 58 and dil, to close main timing or front contacts 352-58 and SLi-6), while contact finger 36 will move out of engagement with contact finger 46 to open back contact 356-46. The upper sides of the contact elements of contact fingers 5S and 60 are normally spaced slightly from a fiat insulating member 62 secured to one end of a spring 6d (FIG. l2) which overlies a similarly extending spring 65. The parts are so proportioned that when the main timing contacts are closed to full compression, these contact elements will engage member 62 and raise it sufficiently to open an auxiliary timing contact 66 (FIG. 9), the function of which will be explained in detail hereinafter. A small permanent magnet 68 is provided on the free end of spring 64 and coacts with a rearwardly bent member 68a of steel on spring 65 to assure both instantaneous opening when the main timing contacts reach full compression, and positive reclosing. The front contact ngers 58 and d0 and springs 6ftand 65 are attached at their opposite ends to similar contact supports 3S also attached, in a manner hereinabove described, to contact block 26. Furthermore, while I have shown only one back contact finger for simplicity in illustrating my invention, it is understood that an additional back contact finger may be added when desired.

As best seen in FIG. l, a stepping magnet generally indicated 7@ comprises a U-shaped backstrap 72 and a winding 74 mounted on a central core 76 afiixed to backstrap 72 as by a screw 77. An armature 78 is pivotally mounted for swinging movement toward and away from core '76 on a pin Sti supported by a bearing support 82 in turn attached, as by bolts 82a to the upper leg 72a of backstrap 72. The armature 78 cooperates with core 76 when winding 74- becomes energized and is provided at its lower end with a depending arm 84 and, near its upper end, with a spacer S6. The spacer 86 is secured to armature 78 by means of screws 87 which extend through aligned holes in spacer 86, a generally L-shaped bracket 8S, and a relatively thin downwardly extending reed spring @il whose function will be explained in detail hereinafter. The lower leg 72b of backstrap 72 is mounted as by screws 91 on a plate 92 including a portion 92a having a downward bend 92h, and also including a portion 92C in the same plane having a curved rearwardly extending segment underlying armature 78. Bolts 93 and 94 are adjustably mounted in the rearwardly extending segment of portion 92e of plate 92. The means on which plate 92 is mounted will be described in detail hereinafter. A coil spring 95 is retained between bracket 8 and bolt 93 and normally biases armature 7S to a nonattracted or open position in which it is shown in the drawings, that is, with the armature separated from the end of core 76. A button 93a formed on one end of s? bolt 93 and a button 88a formed on bracket 88 hold spring 95 in position. During movement of the armature '78 toward core 76, which occurs in opposition to the bias of spring 95, the spring will be slightly compressed and will function to return armature 78 to its normal position when winding 74 becomes deenergized. It will be apparent that the force returning armature 78 to its normal position can be regulated by adjusting the position of ybolt 93 relative to the curved segment of portion 92e of plate 92. It will also be apparent that the other bolt 94, due to its engagement with depending arm S4, as herein shown, acts as a backstop for the armature.

When armature 7S is oscillating, the motion of the armature in one direction is transmitted to a ratchet wheel 96 by means of a pawl 97, the pawl being carried by al leaf spring 98 secured to depending arm 84, and the ratchet wheel being mounted on one end of a drive shaft 99. The pawl 97 is biased downwardly by the resiliency of spring 98 into engagement with the ratchet wheel. Overtravel of pawl 97 is prevented by employing an unthreaded nylon bolty 97a screwed into a tapped hole in portion 92a of plate 92. Rotation of the drive shaft 99 in the direction opposite from that imparted to the drive shaft by the pawl and ratchet mechanism is prevented by a dog 19t) of suitable resilient material secured to the downward bend 92h of the portion 92a of plate 92 by means of a leaf spring lill, and arranged to successively engage the teeth of the ratchet wheel as the wheel is rotated by the pawl.

Attached to the lower end of reed 9d is a weight assembly which together with the reed forms a compound pendulum generally indicated 102 occupying, as illustrated in FIG. l, its normal pendent or biased position. In this position, the center of the mass of the compound pendulum will deiine its vertical axis. The weight assembly comprises a member 104 (FIG. 8) having two metal capsules ,104e joined by an intermediate portion lllib provided, in turn, with a screw-threaded hole 1Mo. Each of the capsules 1Mb is provided internally with a cavity ltllld sealed by a iibrous gasket 104e and a cap screw 1041. The weight assembly also comprises a plurality of weights 196 which function ina well-known manner to partially control the period of oscillation of the pendulum, and further comprises an upwardly projecting latch plate 108 and a similarly projecting member 110 of insulating material, the functions of which will be described hereinafter. The weights 196 are similar and, in the form here shown, and best illustrated in FlG. 4, each comprises a lower slotted or bifurcated portion 1h64: and an upper main portion, the underside of which is adapted to ride on the upper surfaces of the capsules ltllla `which are essentially square cut to assure a firm fit. rIn assembled position, the portion 106:1 of the weight projects downwardly between the capsules 1d4a. A screw 111 extends between the branches of portion lilou and also through aligned holes (not shown) provided in reed 90, the latch plate 108, and member 1li) and threadably engages hole 104C in member 104 to firmly hold the weight assembly in assembled relation with the reed. During normal operation of the relay it may be desirable to adjust the period of oscillation oi the pendulum to a marked degree and, for this purpose, the weights 106 have specifically been provided. It will be noted particularly,y therefore, that the slotted construction of the weights facilitates the aforesaid adjustment by requiring only a slight loosening of the screw in order to remove or replace one of the weights, thus effecting economy of adjustment time by obviating possible appreciable misalignment of the parts comprising the weight assembly.

In the present embodiment of my invention, it has been found that if the reed 90 is constructed of unduly flexible material and suitable damping of the pendulum is not provided, the amplitude of the pendulum may become so great as to exceed the limited space available in the relay and cause the weight assembly to strike the relay frame. If, however, for the purpose of reducing the amplitude of the pendulum, the reed is constructed of a comparatively rigid material, the rate of oscillation of the pendulum may become very rapid and result in increased stresses in the reed. There arises, therefore, in order to conform to the limited amount of space available, the needfor damping the pendulum to enable the use of a relatively short, flexible reed while, at the same time, attaining a slower rate of oscillation in a restricted space than otherwise would have been attainable because of the shorter length of the reed.

To this end, the cavities i10-4d in member 104 are adapted to be partially illed with `a heavy liquid such as, for instance, mercury, or with some other readily shiftable mass. As the pendulum is moved from its pendent position toward its one extremity of oscillation, as in response to movement of armature 78 toward core 76, the liquid will at first tend to gravitate in a reverse direction toward the vertical axis of the pendulum and will, therefore, in a sense, be moving in a reverse direction relative to the pendulum.' Just after the pendulum reverses its direction of oscillation yand commences to move toward its other extrem-ity of oscillation, thek liquid, moving slower relative to the capsule due to its inertia, will buffet the one end of the cavities adjacent to the cap screws and tend to momentarily delay the pendulum, thereby preventing it from attaining considerable momentum at the beginning of its reverse movement. Any appreciable movement of the pendulum toward or away from its other extremity of oscillation will similarly be prevented. Vhus, it can readily be seen that a continuous phase reversal will occur between the movement of the liquid and the movement of the pendulum as the pendulum swings either toward or away from its vertical axis and, as such, will appreciably Vaiiect the moment of inertia of the pendu-lum. It follows, there-fone, that by controlling the level of the liquid in the cavities this arrangement will be effective to dampen a pendlum oscillating in a restricted space.

It is desirable that the pendulum be locked against move-ment during shipment or handling of the relay to revent damage to the reed which might otherwise result if the pendulum is not held immobile while the relay is moved about and, for this purpose, l provide a shipping lock which is automatically actuated when the relay is removed from its mounting base in the manner discussed hereinabove. Heretofore, one customary means oi immobilizing a sensitive and movable pant of a relay has been to apply a shipping screw which locks the part to the frame of the relay, and, as is apparent, requiresa manual operation from which Afailure to apply the screw could result in serious damage. In the automatic lock herein provided, `a generally thin latch arm 112 (iFlG. 2.) is disposed directly above latch plate 1168 and, when the relay is removed from the mounting base, it 'falls automatically, as Ishown in FIG. 2, moving a notch `12rt in the latch arm onto a transverse notch 108s provided in latch plate 1&3. When -the notches 108e and 11211 are thus mutually engaged, any appreciable upward Vertical movement and horizontal movement in any plane of the pendulum is prevented, with kmovement in the horizontal plane being closely restricted to the play in ythe engaging notches. The latch arm H2 is pivota-lly mounted at one end on a pin 11.3 projecting transversely [from a downwardly extending bracket 11d secured to the underside of supporting rib 12e hereinabove described as extending from one of the portions 12b of frame member 12. Adjacent to pin '113 there is showny aligned buttons 11Go and 118e which project from tongues `116 and E18, respectively, of the latch arm 112 and bracket 114, respectively. A coil spring -126 is held in position between buttons 1Mo and 1180. Another bracket, herein designated i212, is secured in a similar manner to the underside of the rib 12e and includes parallel downwardly extending legs 12221 and 12219 which support a cylindrical plunger 123 free to move axially within suitable guide holes provided therein. Secured to one end of this plunger, and projecting loosely through a hole 124 in the portion 12a of frame member 12, is a knob 1215 arranged to contact the forward side 29a of mounting base 2i!l when the relay is plugged in. A substantially rectangular block 126 of insulating material, located intermediate legs 122a and 122b of bracket 122, is tightly threaded on the plunger and is provided at its upper side with a shallow recess 126.1 (FIG. 3). Also mounted in the legs of bracket 122, and shown with its ends split and outwardly bent, Iis a pin 123 disposed above the plunger and located directly within the recess 12651 in block 125. The pin 125 serves as `a guide for block 126 during axial movement of the plunger and also acts to keep the block and plunger from rotating du-ring such movement. A spring 13) placed under compression between block 12-5 and leg 122!) of the bracket 122 surrounds the plunger and, when the relay is not plugged in, biases it to the position in which it is shown Iin lFlG. 2. The knob 125. is provided with an enlarged annular shoulder 12511 which normally engages the inner side of the relay frame to limit the axial movement of the plunger. When the vshipping lock is applied to the pendulum, a bent-up tongue .11219 projecting from the extreme end of latch arm 112 underlies block 126 and acts to prevent the latch arm from being forced upwardly by the weight assembly should the relay be inverted. When the relay is plugged in, the Aplunger will move to the right, as oriented in iFlG. 2, by engagement of knob 125 with the mounting base, and the block will also move simultaneously to a position in which it is no longer overl-ies the tongue v112b on the latch arm, thereby preparing the latch arm for rotational movement. During further movement of the plunger toward the right a nut 131 threaded on its other end wil-l strike the tongue 116 on the latch arm. As the plunger ycontinues its laxial movement, now in opposition to the bias of both springs 121i and 139, the latch arm will be rotated upwardly to a position in which the notch 112a therein is moved out of engagement with the notch .161321 in the latch plate. It will .be obvious that movement of the pendulum in an arc is now permitted. Rotational movement of the latch arm only in the vertical plane is assured due to the extreme end thereof sliding in a guide slot 132 provided in leg '12251 of the bracket I122, as illustrated in HG. 3. For purposes of illustration, the latch arm and block are both shown in FlG. 2 in dashed lines in a conventional manner to illustrate the position they assume when the relay is attached to the mounting base, and they will remain in the positions shown as long as the relay remains on the mounting base. When the relay is detached from the mounting base, the operation of the lock occurs in a reverse order. 'llhat is, the plunger will move toward the left under the bias of spring 130, and the other spring 12d` will act to lower the latch arm until the notches llia and 11251 reengage. .The final lock is provided as block 126 becomes positioned above the tongue 112b on the latch arm. 1t Ifollows, therefore, that the automatic lock of my invention provides full protection from damage for the pendulum whenever the relay is detached for movement or handling or otherwise, without requiring any conscious or active effort on the part of the handler.

The oscillating frequency of the compound pendulum is affected partially by the number of weights 166 as previously mentioned, and by other `factors such as the total mass of the weight assembly, the stillness of reed 9i?, and, additionally, by the stiffness of a downwardly extending leaf type contact spring 134 arranged to be engaged by member I11i), and having mounted at the lower end thereof a contact 134m Mounted between superposed insulating blocks 136, as by screws 137 which threadably engage mounting plate 14, is a fixed contact spring 138 having at its lower end a contact 13851 norn ci mally engaging contact 134e of spring 134. During movement of the pendulum from its pendent position, in response to the energization of stepping magnet "lil, the member 11% will engage spring 134 and move it to a position in which the contact 13de-ldt: is opened, for a purpose which will be made clear as the description proceeds. To prevent interference to movement of spring 1341 when it yields to the pressure of member 110, the mounting plate 14 is provided with a notch 139 (KFIG, l) into which spring 134 may swing with clearance. The other end of the spring 134 is clamped between superposed insulating blocks 141i which are secured as by screws 141 to one side of a pole piece 142 forming a part of a magnetic clutch which I will now describe.

This magnetic clutch, as best seen in FIGS. 5 and ll, comprises pole piece 142 which projects from one end of a core 1414 having a winding 146 mounted thereon in any well-known manner, and which has internally a central aperture 11426: extending longitudinally from end to end thereof and in continuation to the end of pole piece 142. The pole piece 142 is formed round at the side opposite to the side thereof receiving screws 1411, and is iiat 4at its upper and lower sides. The portion 92a of the plate 92 is fixed to the upper side of pole piece 142 by means of suitable screws (not shown) extending therethrough yand through an intermediate washer 16S and becoming threadably engaged to pole piece 142. The plate 92 is mounted on pole piece 142 before the mounting of the stepping magnet "i0 thereon. At the lbottom of pole piece 14E-2 screws 149 extend upwardly through the mounting plate and thence through a washer 15d and threadably engage the underside of pole piece 1-12 to rigidly attach the pole piece to the mounting plate. A pair of annular bushings 151 and 152 are pressed in fiixed relation into the core at opposite ends `of the aperture 1Min therein. The shaft 99 is loosely journaled in these bushings and is provided at its end opposite to the end thereof connected with the ratchet wheel with a pinion .154. The outer end of bushing 152 projects axially outside of the core and is there formed with a bearing surface 1526:. A gear 156 concentric with the aperture in core '141i is rotatably mounted on the bearing surface of bushing 152 and is secured by rivets 15'7 to a disk-shaped pole piece y1525 spaced from the core by a suitable air gap which, as is apparent, permits rotation of pole piece 15d about the axis of the core. Preferably, the radius of pole piece `153 is substantially equal to the radius of the rounded portion of the other pole piece 142. pole piece 153 extends slightly below the upper surface of the mounting plate and, in order not to hinder rotation of pole piece 158, the mountting plate is formed slightly reduced in width commencing at a point designated 1611 substantially directly beneath pole piece 158. Disposed substantially beneath both of the pole pieces, and formed with a concave surface 16261 conforming essentially to the shape of the curved periphery of pole pieces 1412 and 158, is a magnetizable clutch armature 15?. biased normally by its Weight out of engagement with the pole pieces, and arranged to simultaneously engage pole pieces 142 and 153` to accordingly prevent pole piece 15S from rotating when winding 146 becomes energized. A generally U-shaped member 163 is attached to the underside of the mounting plate by the same screws 149 which fix the pole piece 142 to the mounting plate, and compris-es parallel legs 163:1 and 163i) (see FIG. 5) which function as backstops for the clutch armature. When desired, a hard plating such, for example, as chromium plating, wi ich is characterized by its resistance to wear, may be deposited directly on the concave portion of armature `1d?. `and the periphery of pole piece 158.

The clutch armature 162 is mounted on a pileup of insulating blocks 164 clamped by means of screws 165 against the underside of the clutch armature. Mounting screws 165 have the usual insulating sleeves 166 thereon. {Two tlat strips 16S and 170 of relatively ilexible material (FIG. serve as support members for armature 162, and also as members of auxiliary contacts described later. As best seen in FIG. 1, both of these strips are secure-ly clamped at their one end between the blocks 164, the one strip 166 being clamp@ at its other end between other Iinsulating blocks 172 similarly secured to the underside of the mounting plate, and the other strips 17d` being similarly clamped at its other end between the aforementioned blocks 1316. A contact finger 174 (PllG. l) is also clamped between the blocks 136 and is provided` with a contact element 174s intended to cooperate with a contact element 17de provided on the underside of strip 171i to close the contact Titia-174e only when the clutch armature occupies its gravity-biased position, as shown in the drawings. It is pointed` out, therefore, that .the strip 17u not only functions to mechanically provide support for the clutch armature but may equally be useful for simultaneously controlling an electrical circuit, of any suitable choice, which monitors the performance of the clutch armature. 'For example, as contemplated in my invention, this electrical circuit may comprise contact 170a174a electri* cally connected in series with back contact 36-46 to form a check circuit of the type well known in the art tor checking the readiness of certain parts of the relay for another cycle of operation.k With this arrangement, contact Utta-174e also serves as an instantaneously opening contact to open the check circuit immediately upon energization of winding 146.

A planetary gear assembly generally indicated 176 is located at a point between the magnetic clutch and pinion 154. The pinion 154 (see FIGS. 5 and 13) meshes with a gear 178 secured to one end of a countershaft 150 journaled in a counterwc'ight 181 through which, near its upper end, the drive 99 loosely projects. Attached to the other end of lthe countershaft is a sun gear 182 which meshes with the gear 156. The sun gear 182 is adapted to rotate about gear 156 when the pole piece 158 is stopped against rotation, thereby effecting a change in the angular position of the counterweight. The parts are so arranged that when armature 162 becomes disengaged from pole piece 15S, the planetary gear assembly and, hence the counterweight will return -to its normal position, in which it is shown in the drawings, in preparation for the next timing operation. When the counterweight occupies its normal position its rearward side abuts upon the mounting plate along the surface of the mounting plate reduced in width, as described hereinabove.

As best seen in FIGS. 5 and 6, a generally rectangular bracket 184 extends upwardly from the mounting plate and is attached thereto at its base by screws 134:1. A bolt .186 is tightly fastened by means of a nut 187 to one end of a bracket 18S secured, in turn, at its other end to the top `of bracket 134 by means of screws 189. Bolt 186 terminates at its other end in a hub 196 (FlG. 13) concentric with shaft 99 provided with a central hole 191m in which the extreme end of shaft 99 is dispo-sed for supporting it. It 'will be understood'that when thus fastened to bracket 1558 bolt 186 is not capable of rotation. A pinion 192 is rotatably mounted on bolt 186 and is connected with a Contact arm 194 normally spaced from operating ladder Si) by a predetermined angular distance and connected, in turn, with a segment 196 provided with a scale. As is obvious, the pinion 192, arm 194, and segment 196 are arranged for concurrent rotation with each other on the bolt. The pinion 192 forms a part of a rack and pinion larrangement for varying the position of contact arm 194 relative to the operating ladder 50, and which l will now describe.

The rack and pinion arrangement, as best seen in FIG. 13, includes a rack bar 198 having teeth meshing with pinion 192 and also having an upwardly bent leg k198er through which a screw 211i) extends with clearance. A bushing 2112 is afxed to screw 21N) by means of a rivet 2% (FiG. 6i). The screw Ztl() extends loosely at a point intermediate its ends through an upright portion 204:1 (FIG. 13) of a plate indicated generally by the reference character 2114. A locking nut 206 is firmly affixed in a well-known manner to portion 204e of plate 204 and provides a threaded member in which screw 26N) may be turned. The plate 204 is provided with two downwardly extending legs 2114!) and Ziidd, the one leg 204i: having a hole through which the extreme end of Ithe drive shaft loosely projects, the other leg 204:1 being adapted to contact the upper side of a segment 221 (FIG. 6) on the operating ladder. Iln this position, leg 2040? pulls the ladder `downwardly against the bias of the movable contact lingers and supporting spring 4S causing the ladder to bend them slightly through the coaction of their mutually adjacent portions. Consequently, ladder 50 is biased in an upward direction. However, it will be readily apparent that upward movement of the operating ladder can be executed only by ldiscontinuing the operative connection between leg kZtltd and segment 221.

A platform portion 264e of plate 204 is secured to the upper side of the counterweight by means of suitable screws 2157. The screw 213i) is disposed concentric with a tool 2118 (FlG. 6) slidably mounted in a mit 299 amxed to portion 12a of the relay frame in an opening 210 provided therein, and is adapted to be turned thereby. The end of the tool adjacent to the head of screw 201! terminates in a flat, thin tip 2118er. The tool 206 is arranged to be guided during its axial movement by means of an L-shaped bracket 2112 held against the frame by lnut 209. A downwardly extending member 213 is suitably attached to bracket 212 and acts as a support for the tool to keep it in alignment with screw 211i). A coil spring 214' surrounds the shank of the tool between the member 213 and a washer 216 rigid with the tool. Spring 214 is arranged to be compressed following any movement of the tool toward the left and acts to return it to its normal position, in which it is shown `in thedrawings. With the parts constructed in this manner, the opening 21d is at lall times sealed `against the entrance of foreign matter. From the above, it follows that when screw 200 is turned, for instance, so as to rotate pinion k192 in a clockwise direction, as oriented in FIG?. 7, the travel of contact arm 194 necessary to engage the operating ladder 'will be decreased. rOn the other hand, when screw 200 is turned in the opposite direction, it will be apparent that the angular distance separating the contact arm and the operating ladder will be increased. A pointer 218 is fastened to portion 2114er of plate 204 by looking nut 206 and segment 196 will, therefore, move relative to the pointer as the position of contact arm `1.94 with respect to the operating ladder is varied. The reason for varying the relative position of Ithe contact arm and the operating ladder will be explained in detail hereinafter.

Referring now to the ywiring diagram for the relay shown in FIG. 14, the two windings of the stepping magnet and the magnet clutch referred to hereinabove are designated by their reference characters 74 and 146, respectively. The auxiliary timing contact 66, and the contact springs forming the normally closed 'contact 1Mo-38a are similarly designated by Itheir respective reference charac-ters. Current is supplied to the Windings 74 and 146 from a suitable source, such as `a` battery 219, having positive and negative terminals, overan externally operated circuit controller 221i which may be operated in any suitable manner.

Als shown in the drawings, circuit controller 22() is open so that the windings 74 and 146 are deenergized. The armature 78 is therefore swung away from core 76 so that the contact 134a-`138a (FIG. l) and back contact 36--46 (FIG. 6) `areclosed, while bothfront conaraaers tacts 32-53 and 354-60 are open. As previously mentioned, -the clutch armature 162 is self-biased to its normal position.

I will now assume that with the parts in the positions just described, circuit controller 22? becomes closed. Winding ldd will be connected directly across the terminals of the battery and will, therefore, become energized. At the same time, the winding 74- of the stepping magnet will be connected with the battery over a circuit which includes the auxiliary timing contact 66 and the contact llia-la and will, therefore, also become energized. As a result, the clutch armature is moved into engagement with the pole piece S to temporarily immobilize it. Movement of armature '73 to the right, as oriented in FIG. l, imparts mechanical energy to pendulum 102 causing the pendulum to swing to the right whereby the member llt) attached thereto disengages or opens the contact 13de-433g. Winding '74 of the stepping magnet will then become deenergized and its flux field will decay. After the momentum of the pendulum is expended, it will start to swing in the opposite direction due to the action of gravity on the pendulum, and because of the biasing force of spring 95 acting to reverse the movement of armature 7d. As armature 73 returns toward its nonattracted position, mechanical energy is again imparted to pendulum 1.62 causing it to reverse its direction of oscillation whereupon the contact l3da-l38a will again become closed. With the Contact 13451-43361 closed, the winding '7d will again become energized and the cycle of operation will be repeated.

Each time armature 73 is swung toward core 76, ratchet Wheel 96, drive shaft 99, and the pinion 154 are rotated through a small arc due to the pawl and ratchet mechanism described hereinbefore. Since the clutch armature is now swung toward pole piece I Sl, gear ld is prevented from rotating. It will be apparent, therefore, that the sun gear will climb around gear i556 causing the counterweight llll and, hence, the plate 2&4, to rotate in a clockwise direction, as oriented in FlG. l. Concurrent with the rotation of plate Eil-l, the operating ladder will travel upwardly. The parts are proportioned so that when the biasing force of the movable contact lingers and supporting spring d is completely expended, front contacts 32-58 and Slt-oil will remain open, whereas back contact 'S4-36 will have been opened. Because of the ixed engagement between the screw 2d@ and the portion 2Mo of the plate 204, and the engagement of the teeth of the rack bar w3 with the pinion 192, the pinion 192 and, hence, contact arm 19d, will also be rotated in a simi.ar direction at a constant predetermined rate. As angular movement of the Contact arm continues, Contact arm ld will be rotated through an arc greater than that initially' separating it from operating ladder Sil, and will engage the operating ladder and move it upwardly an extent suihcient to now close front contacts S-SS and 3ft-6i?. Contact arm 19d will continue to be rotated through a slightly greater arc causing insulating member 62 to move upwardly to open the auxiliary timing contact d6, as described hereinbefore. The opening of the auxiliary timing contact opens the energizing circuit of winding 7d to stop the action of the stepping magnet. The planetary gear assembly 176 remains in its elevated position and holds the contacts 352-58 and 3d-6tl closed until the circuit controller 220 is interrupted externally, whereupon the control circuit for winding lid-6 will be opened and winding 146 will, therefore, become deenergized. Armature 162 will, therefore, return to its biased position and, in turn, the planetary gear assembly will return to its normal position due to its weight, in readiness to complete a new timing operation. The rotation of the planetary gear assembly during this portion of its movement will, of course, be transmitted to plate 264 and, just prior to the time the planetary gear assembly reaches its normal position, leg Ztl/td of plate 2M will reengage segment 221 vof ladder Sil and again force the ladder downwardly. 0n

l2; account of this enforced downward movement of the operating ladder, reliable assurance is provided that the front contacts have been opened, the back contact has been closed, and also that the operating ladder is positioned in readiness for the next timing operation.

As will readily be understood, the length of the arc through which Contact arm ld has to move from its normal position in order to reach the operating ladder may be varied by varying the relative position of the contact arm with respect to the operating ladder in the manner which has previously been described. It will be apparent, therefore, without opening the case of the relay, that the time which elapses between the closing of circuit controller 22) and the closing of front contacts 32-58 and 345-6@ may be adjusted to any desired value. To illustrate the facility of adjusting the duration of the timing operation, l have shown, in FlG. 7, the contact arm llt-t positioned to Contact the operating ladder in the shortest possible time and, it will be apparent, that to change the position of the contact arm in the present embodiment of my invention only a few turns of the screw 2li@ is required.

The time interval required for the operation of the relay may be indicated by the position of pointer 218 on the scale provided on segment 196 by suitably calibrating the scale so that the graduations thereon correspond to the correct time intervals.

For reasons described hereinabove, it is desirable that excessive movement of certain parts of the relay be prevented while the relay is detached from the mounting base and, for this purpose, l provide a locking mechanism for the planetary gear assembly which functions in a manner similar to the operation of the automatic lock hereinabove described for use in connection with the pendulum 162. The planetary gear assembly which includes the counterweight, and the related parts of the relay cooperating with plate 204 are, obviously, comparatively hei Vy. When the relay is removed from its mounting base this weighted mechanism is free to move and, should the relay be inverted as may occur during handling or shipment, the weighted mechanism could easily abruptly actuate the operating ladder and perhaps damage the contacts that the ladder normally operates. To prevent such an occurrence, I provide a screw 222 (FIGS. 6 and 13) projecting rearwardly from the counterweight, whereby when the relay is detached from its mounting base, this screw is positioned directly above a relatively thin rectangular stop member 22d, best illustrated in FIG. l0. Rotational movement of the counterweight and, hence, of the planetary gear assembly, is thereby at times limited to the space between screw 222 and the upper edge of the stop member. The stop member 224i extends downwardly through a slot 225 formed in the mounting plate la and is provided at its lower end with an opening 22Min through which one end of a plunger or rod 225 loosely projects. rlhe under side of the upper or larger portion of stop member 224 rests upon the upper side of the mounting plate to thereby provide a fulcrum for the stop member. The other end of plunger 226 is provided with a head 223 which projects through another opening 229 in the vertical portion of frame member l2, which head is adapted to engage the forward side Ztlrz of the mounting base 20 when the relay is attached to the mounting base, substantially as explained hereinbefore. A washer 23d is secured to the plunger in any suitable manner herein not shown, and acts to limit axial movement of the plunger in the direction of the mounting base. Riveted or otherwise secured to the upper side of mounting plate 1d is a curved bracket 231, the upper leg .Sla of which is provided with a button 232. A similar button 23d is provided on the side of the stop member facing bracket 2.3i. A coil spring 233 having itsaxis parallel to but spaced from the longitudinal axis of plunger 226 is mounted in position on the buttons 232 and A disk 236 is mounted on plunger 226 by means of a pair of nuts 237 and is shown spaced slightly from the underside of the mounting plate. Disk 236 serves to prevent stop member 224 from moving away from its fulcrum point by engaging the under side of the mounting'plate in response to any appreciable upward bending of plunger 226. When the relay is attached to the mounting base, the plunger is moved toward the left, as viewed in FIG. 6, and stop member 2.24 pivots on its fulcrum and takes up substantially the oblique position illustrated (FIG. 6) in the dashed line presentation thereof, thereby preparing the planetary gear assembly for rotation. During this movement of the stop member, the spring 233 will be compressed slightly and thereafter act to return the stop member to its position approximately perpendicular to the plunger 226 when the pressure between the head 228 and the mounting base is relieved. The parts are so proportioned that should the stop member assume its position normal to the plunger in advance of the counterweight returning to its normal position, the impact of the screw 222 against the forward upper edge of the stop member, due to the downward momentum of the counterweight, will provide suiicient force to compress spring 233 and thereby enable the screw to` assume its position over the stop member. It will be apparent, therefore, that no manual operation is required to immobilize the weighted mechanism embodied herein during handling or other movement of the relay, and that application of the locking mechanism will occur instantly at the start of such handling without any reflection on the part of the handler.

From the foregoing, it will be apparent that I have provided a time element relay in which the time interval between the energization of the relay and the closing of the front contacts of the relay can be adjusted by the use of simpler and less expensive parts than heretofore provided for the same purpose.

One advantage of the relay embodying my invention is that when the relay is energized the relatively large contacting surface areas of the armature lo?. and the core members M2 and 153 are held together by a considerable and practically constant pressure, and, to move one surtace relative to another, it is first necessary to deenergize the relay which is not an undesirable expendient, since, as is apparent, the deenergization of the relay follows the completion ofthe timing operation. There will, therefore, be no significant movement of the parts of the clutch relative to one another during the timing operation ot the relay due to their magnetic interlocking. Furthermore, my invention 05ers a satisfactory solution to a hitherto troublesome problem in that periodic adjustment of the parts of the clutch will'be obviated.

Another advantage of my invention is that parts of the relay that tend to rotate or oscillate are arranged to at times have their motion restricted to ensure maximum reliability of operation following reattachment of the relay to its mounting base after inspection or handling of the relay, or the like.

Although I have herein shown and described only one form of relay embodying my invention, I do not desire to limit myself to the particular relation of its parts or other details of construction or arrangement, as various changes may be made within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1, An electromagneticy clutch assembly comprising a stationary core having a winding mounted thereon, a irst pole piece projecting from one end of said core, a second pole piece at the other end of said core mounted for rotation about the longitudinal axis of said core, and means normally biased apart froml said first and second pole pieces and movable into engagement with said pole pieces to prevent said second pole piece'from rotating with respect to said first pole piece when said winding becomes energized.

disk-shaped second pole piece spaced from the other end of said core by an air gap and mounted for rotation about the longitudinal axis of said core, and an armature kbiased normally by its own weight apart from said iirst and second pole pieces andr provided with a concave portion adapted to engage the' periphery of said iirst and second pole pieces when said winding becomes energized to prevent said second pole piece from rotating.

3. An electromagnetic clutch assembly comprising, a core having an opening extending completely therethrough along its longitudinal axis, a winding mounted on said core, a first pole piece projecting from one end of said core and having an opening therein whose center aligns with the opening in said core, a second pole piece located adjacent to the other end of said core and mounted for rotational movement about the longitudinal axis of said core, said second pole piece having a central opening which aligns with said other aligned openings, said aligned openings forming a passageway extending from one end of said iirst pole piece and through said core to a corresponding end of said second pole piece, and means mounted for movement from a gravity biased position out of engagement with said iirst and second pole pieces to a position into engagement with said pole pieces when said winding becomes energized for preventing said second pole piece from rotating.

4. A clutch assembly including electromagnetic apparatus comprising, in combination, a iixed core provided midway between its ends with a winding, a iirst substantially annular pole piece projecting from one end of said core', a second annular pole piece located at the other end of said core and spaced therefrom by an air gap, bearing means projecting from rsaid other end of said core for `mounting said second pole piece rotatably about the said armature being engageable with the peripheries of said rst and second pole pieces in response to the energization of said winding, thereby immobilizing said second pole piece during the period of said energization. j

5. An electromagnetic clutch assembly comprising a hollow core having a winding mounted thereon, a bushing mounted in said core in alignment with the longitudinal axis thereof and having a portion projecting outwardly from one end of said core, said projecting portion of said bushing forming a bearing surface, a flat and generally annular first pole piece rotatably mounted on the bearing surface of said bushing, a second pole piece projecting from the other end of said core, said second poie piece having a hole therethrough coaxial with the longitudinal axis of said core, a resilient and generally lealiilze member extending in a plane normal to the longitudinal axis of said core and disposed spaced `from and substantially below said iirst and second pole pieces, and means mounted on said leatlike member operable for engaging said pole pieces for preventing rotation of said first pole piece when said winding becomes energized but being norm lly gravity biased out of engagement therewith in the deenergized condition of said winding.

6. An electromagnetic clutch assembly comprising a core and a winding mounted on and midway between the ends of said core, a pole piece spaced slightly from one end of said core and mounted for rotational movement about the longitudinal axis of said core, an armature disposed in a normal position biased away from said pole piece and movable into engagement with said pole piece such to prevent its rotation at times when said winding is energized, an electricallyy conductive and generally resilient and leailike first member disposed alongside said pole piece and fixed at one end thereof and at its free snaar-srs end secured to said armature, insulating means for insulating said first member from said armature, a resilient and also conductive second member fixed at one end and extending longitudinally alongside said first member, and a contact carried by each of said members for cooperation only when said armature occupies its normal position.

7. An electromagnetic clutch assembly comprising a core having a winding mounted thereon midway between its ends, said core provided at its one end with a projecting first pole piece and at the other end with a second pole piece spaced therefrom by an air gap and mounted for angular movement about the longitudinal axis of said core, and an armature disposed normally away from said first and second pole pieces and movable into direct engagement therewith in such a manner to complete a closed circuit for the magnetic flux attempting to iiow when said winding becomes energized, whereby during the period of said energization said second pole piece is prevented by means of magnetic locking from rotating with respect to said first pole piece.

8. In a timing relay, the combination with stepping means capable of being alternately actuated and deactuated at a constant and predetermined rate in such manner to provide consecutive and regularly intermittent motion impulses, of a hollow and generally cylindrical core having a winding mounted thereon, a busing mounted centrally in the hollow space in said core and having a tubular portion projecting outwardly from one end of said core, a shaft journaled in said bushing and projecting at each end well beyond the ends of said core, means on one end of said shaft located adjacent to the other end of said core connecting with said stepping means for actuating said shaft serially in accordance with the rate of said motion impulses, a pole piece rotatably mounted on the tubular portion of said bushing and disposed with its one end spaced from said core by a suitable air gap, a second gear rigid with said pole piece on its other end, magnetizable means biased normally away from said pole piece but movable into frictional contact with said pole piece in response to the energization of said winding such to render it immovable, a timing contact, and planetary gear means connected with said gear and operatively connected with the other end of the shaft for operating said contact after a predetermined time interval following the energization of said winding.

9. A self-timing relay comprising a stepping magnet cooperating with an armature movable between a first position and a second position in response to the energization of said stepping magnet, a clutch magnet including a core having a winding thereon, said core having an aperture therethrough whose axis aligns with the longitudinal axis of said core, a bushing mounted in the aperture in said core and having a tubular portion projecting outwardly from one end of said core, a pole piece rotatably mounted on the tubular portion of said bushing and disposed with its one end spaced from said core by an air gap, a first gear rigid with said core on its other end, a shaft journaled in said bushing extending in said aperture and projecting at one end beyond said first gear and at the other end beyond the other end of said core, stepping means operatively connected with said other end of said shaft and With said armature for actuating said shaft in response to movement of said armature, means cooperating with said pole piece only when said winding becomes energized for preventing its rotation, a timing Contact, and planetary gear means cooperating with said gear and being operatively connected with said one end of said shaft for actuating said contact after the expiration of a predetermined period of time following the energization of said winding.

10. In a self-timing relay having a contact adapted to be operated after the expiration of a time interval following the initial energization of said relay, the combination with a stepping magnet cooperating with an armature movable between a first position and a second position in response to the energization of said stepping magnet, and

a pawl operatively connected with said armature actuated in response to the energy imparted thereto by movement of said armature of a hollow and generally cylindrical core having a winding mounted thereon, a bushing mounted in the hollow space in said core and having a tubular portion projecting outwardly from one end of said core, a shaft journaled in said bushing such that its extremities project beyond the ends of said core, a rst gear on the end of said shaft adjacent to the projecting portion of said bushing, means on the other end of said shaft connecting with said pawl for actuating said shaft in response to the actuation of said pawl, a pole piece rotatably mounted on the projecting portion of said bushing disposed with its one end spaced from said core by a suitable air gap, a second gear rigid with said pole piece on its other end, magnetizable means biased normally away from said pole piece and movable into frictional contact with said pole piece in response to the energization of said winding in such a manner to prevent it from rotating, and planetary gear means cooperating with said rst and second gears for operating said Contact after a predetermined time interval following the initial energization of' said winding.

1l. In a relay adapted for plug-in mounting in a mounting base, the combination of a frame member on said relay with the side of said frame member outside of said relay substantially abutting upon a forward side of said mounting base when said relay is attached to said mounting base, said frame member having an opening therein adapted to be aligned with the forward side of said mounting base, said relay having an o erating element movable between a normal position and an operated position, a plunger slidably mounted in said opening, one end of said plunger projecting slightly outside of said relay whereby when said relay is attached to said mounting base said plunger abuts against the forward side of said mounting base and moves axially further into said relay, and means controlled by said plunger for preventing movement of said element from its normal to its operated position when said relay is detached from said mounting base but automatically permitting said movement in response to said axial movement of said plunger.

12. In a relay adapted for plug-in mounting in a mounting base, the combination of a frame member on said relay with the side thereof outside of said relay being substantially flush mounted against the forward side of said mounting base when said relay is attached to said mounting base, said frame member having an opening therethrough adapted to be aligned with the forward side of said mounting base, a plunger slidably mounted in said opening having a portion projecting slightly outside of said relay and a considerably longer portion extending in said relay, said plunger contacting the forward side of said mounting base and moving axially inwardly when said relay is attached to said mounting base, said relay having a part movable between a first position in which its movement is restricted when said relay is detached from said mounting base and a second position, and means effective in response to said axial movement of said plunger for releasing said part and accordingly permitting 'its movement from its first to its second position.

13. In a timing relay adapted for plug-in mounting in a mounting base, the combination of a frame member on said relay with the side thereof outside of said relay disposed substantially in engagement with the forward side of said mounting base when said relay is attached thereto, said frame member having an opening therein adapted to be aligned with the forward side of said mounting base, a stepping magnet and an armature movable relative thereto between a first position and a second position in response to the energization of said stepping magnet, a gear train operatively connected with said armature and including a clutch assembly, means for braking said clutch assembly, a planetary gear assembly arranged to rotate about said clutch assembly in response to the 17 continued actuation of said gear train when said clutch assembly is braked, a plunger slidably mounted in said opening projecting slightly at one end outside of said relay a predetermined extent, whereby when said relay is attached to said mounting base said plunger engages the forward side of said mounting base and .moves axially further into said relay, and means cooperating with the inner end of said plunger and responsiverto said axial movement thereof for permitting said planetary gear assembly to rotate only when said relay is attached to said mounting base.

14. In combination with a relay comprising a frame member having an opening therethrough adapted for mounting on a mounting base with the side of said frame member outside of said relay substantially abutting upon the forward side of said mounting base whenever said relay is attached to said mounting base, a part rotatable between a tirst position and a second position, an axially movable plunger slidably mounted in said opening, said plunger including a relatively short portion in said opening adapted to engage the forward side of said mounting base when said relay is attached to said mounting base therebyfcausing said plunger to move axially inwardly in said opening, and a latch member cooperating with the end of said plunger inside of said relay such to prevent said part from rotating from its first to its second position except when said plunger is moved axially inwardly in said opening. n

15. The combination in a relay adapted for plug-in mounting in a mounting base, of a frame member on said relay having the side thereof outside of said relay substantially ilush mounted against the forward side of said mounting base when said relay is attached to said mounting base, said relay having a part mounted for rotary movement between a trst extreme position and a second extreme position, said frame member provided with an opening adapted to be aligned with a preselected point on the forward side of said mounting base, a plunger slidably mounted in said opening and projecting at one end outside of said relay when said relay -is detached from said mounting base, whereby when said relay is attached to said mounting base said plunger engages said mounting base and is moved thereby axially inwardly in said opening, a latch 'member extending in a plane generally perpendicular to the longitudinal axis of said plunger secured at its one end to the inner end of said plunger and at the other end cooperating with said part in such a manner to prevent said part from rotating unless said plunger is lirst moved axially inwardly, and biasing means for yieldably biasing said latch member toward the posi tion in which rotary movement of said part is prevented.

16. The combination in a relay adapted for plug-in mounting in a mounting base, of a frame member on said relay having the side thereof outside of said relay substantially flush mounted` against the forward side of said mounting base when said relay is attached to said mounting base, said relay having a part mounted for rotary movement between a tirst extreme position and a second extreme position, said frame member provided with an opening adapted to be aligned with a pre-selected point on the forward side of said mounting base, a plunger slidably mounted in said opening and projecting at one end outside of said yrelay when said relay is detached from said mounting base, whereby when said relay is attached to said mounting base said plunger engages said mounting base and is moved thereby axially inwardly in said opening7 a latch member extending upwardlyrin a plane substantially perpendicular to the longitudinal axis of said plunger and secured at its lower end to the inner end of said plunger and at its upper end vcooperating with said part in such a manner to prevent said part from rotating unless said plunger is first moved axially inwardly, and biasing means parallel to and spaced from the longitudinal axis of said plunger acting against said latch member for yieldably biasingfit to the position in which rotary movement of said part is prevented.

17. The combination in a relay adapted for plug-in mounting in a mounting base, of a frame memberon said relay having the side thereof outside of said relay substantially llush mounted against the forward side of said mounting base when said relay is attached to said mounting base, said relay having a part mounted for rotary movement between a lirst extreme position and a second extreme position, said frame member provided with an opening adapted to be aligned with a preselected point on the forward side of said mounting base, a plunger slidably mounted in said opening and projecting at one end outside of said relay when said relay is detached from said mounting base, whereby when said relay is attached to said mount-ing base said plunger engages said mounting base and is moved thereby axially inwardly in said opening, a -mounting plate provided with an opening directly above the inner end of said plunger, a latch member disposed in said opening and provided with oppositely disposed outwardly projecting shoulders engaging the upper side of said mounting plate whereby said latch member is pivotally mounted on said mounting plate, said latch memberfcooperating at its lower end with said plunger such thatkit is pivoted on said mounting plate in response kto axial movement of said plunger, the upper end `of said plunger being closely spaced from said part when said relay is detached from said mounting base in a rst position such to prevent said part from moving from its first to its'second position, but being pivoted in response to axial inward movement of said plunger to a second position in which rotation of said part is permitted, and biasing means disposed parallel to and spaced from the longitudinal axis of said plunger for yieldably biasing said latch mem-ber toward its tirst position.

18. In combination with a relay comprising a frame member adapted for mounting on a mounting base with the side of said frame member outside of said relay substantially abutting upon the forward side of said mounting base wheny said relay is attached to said mounting base, stepping means capable of being alternately actuated and deactuated at a constant and predetermined rate for providing consecutive and regularly intermittent motion impulses, a gear train operatively connected with said stepping means actuatedfin response to said motion impulses and including a clutch assembly, means for braking said clutch assembly, a planetary gear assembly mounted for rotation about said clutch assembly between a first position and a second position in response to the continued actuation of said gear train when said clutch assembly is braked, said frame member having an opening adapted to be aligned with a preselected point on said mounting base, a plunger slidably mounted in said opening and projecting at one end outside of said relay and at the other end alongside said planetary gear assembly, whereby when said relay is attached to said mounting base said plunger is moved axially inwardly in said opening by means of said mounting base, a thin and generally rectangular latch member operatively connected at one end to the inner end of said plunger and extending transversely therefrom, said latch member cooperating at its other end with said planetary gear assembly and movable between a first position in which it prevents said planetary gear assembly from rotating from its first to its second position and a second position in response to said axial movement of said plunger in which rotation of said planetary gear assembly is permitted, and means for yieldably biasing said latch member toward its rst position.

19. In combination with a relay comprising a frame member adapted for mounting on a mounting base provided with a vertical and generally flat forward sidewith the side of said frame member outside of said relay being substantially tlush'mounted against the forward side of said mounting ybase when said relay is attached thereto,

a compound pendulum, a generally thin latch arm of relatively long dimension pivotally mounted at one end for movement between a first position operatively connected with said pendulum such to prevent it from oscillating and a second position away from said pendulum, and means automatically effective when said relay is attached to said mounting base for moving said latch arm from its first to its second position.

20. In combination in a relay comprising a frame member adapted for mounting on a mounting base provided with a vertical and generally flat forward side with the side of said frame member outside of said relay abutting substantially upon the forward side of said mounting base when said relay is attached thereto, a compound pendulum including a latch member at its lower end extending upwardly in a plane generally parallel to the vertical axis of said pendulum, a generally thin latch arm of relatively long dimension extending above said latch member in a plane generally perpendicular to the vertical axis of said pendulum when said relay is detached from said mounting base, said latch arm -being pivotally mounted at one end farthest from said mounting base for rotation between a first position in engagement with said latch member for restricting oscillatory movement of said pendulum and a second position away from said latch member, means for yieldably biasing said latch arm downwardly toward its first position, and means automatically effective when said relay is attached to said mounting base for moving said latch arm upwardly from its first to its second position.

21. In a relay adapted for plug-in mounting in a mounting base, the combination of a frame member on said relay with the side thereof outside of said relay substantially abutting upon the forward side of said mounting base when said relay is attached to said mounting base, said frame member having an opening therein 4adapted to be aligned with the forward side of said mounting base, an axially movable rod-like member slidably mounted in said opening projecting slightly at one end outside of said relay, said rod-like member engaging the forward side of said mounting base when said relay is attached to said mounting base and being moved axially inwardly thereby, a pendulum whose vertical axis is disposed perpendicular to the longitudinal axis of said rod-like member, a latch arm pivotally mounted at one end and `at the other end having means for interlocking it with said pendulum, and means movable with said rod-like member for rotating said latch arm about its axis of rotation sufliciently to` discontinue the interlocking relation between said pendulum and said latch arm when said relay is attached to said mounting base.

22. In combination with a relay comprising a frame member adapted for mounting on a mounting base with the side of said frame member outside of said relay substantially abutting against the forward side of said mounting base when said relay is attached to said mounting base, a compound pendulum including a weight at its lower end, said frame member having an opening therein adapted to be aligned with the forward side of said mounting base, an axially movable plunger slidably mounted in said opening having a portion projecting outside of said relay yand a considerably longer portion extending inside said relay above said weight in a plane generally perpendicular to the vertical axis of said pendulum, whereby when said relay is attached to said mounting base said plunger engages the forward side of said mounting base and is moved axially thereby inwardly in said opening, a latch member extending upwardly from said weight formed with a first notch in its upper edge, a rotatably mounted latch arm having a relatively long dimension parallel to and extending in a plane generally coplanar with the longitudinal axis of said plunger, said latch arm having a transverse second notch in its lower edge sufficiently close to said latch member to allow said first and second notches to become mutually engaged when said relay is detached from said mounting base, and means on said plunger effective in response to said axial inward movement of said plunger for rotating said latch arm suciently to discontinue the mutual engagement of said first and second notches.

23. In combination with a relay comprising a frame member adapted for mounting on a mounting base with the side of said frame member outside of said relay being substantially flush mounted against the forward side of said mounting base when said relay is attached to said mounting base, a compound pendulum carrying at its lower end `a latch member which extends upwardly in a plane generally parallel to the vertical axis of said pendulum, said latch member having a first notch formed in its upper edge, said frame member having an opening therethrough adapted to be aligned with the forward side of said mounting base, an axially movable plunger extending in said opening, one end of said plunger projecting a predetermined distance outside of said relay and at the other end extending above said latch member in a plane generally perpendicular to the vertical axis of said pendulum, whereby when said relay is attached to said mounting base the plunger is moved axially further into said relay,

a manually adjustable nut threaded on and projecting beyond said other end of said plunger, a latch arm having a relatively long dimension rotatably mounted at one end adjacent to said nut and extending above said latch member generally parallel to the longitudinal axis of said plunger, said latch arm provided in its lower edge with a second notch transverse to and substantially directly above said first notch, means effective when said relay is detached from said mounting base for yieldably biasing said latch arm into engagement with said latch member in such a manner that said first and second notches become mutually engaged, and a projecting portion on said latch arm disposed adjacent to and in alignment with said nut with the distance separating said nut and said projecting portion being not more than substantially the distance said plunger projects outside of said relay, said nut engaging said projecting portion on said latch arm when said plunger moves axially whereby said latch arm is rotated to a position in which the mutual engagement of said first and second notches is discontinued.

24. In a timing device, the combination with a pendulum including a reed normally disposed in a vertical position and being pivotally mounted at its upper end for swinging movement on one side of its vertical axis to a iirst extreme position and on the other side to a second extreme position, of a body secured to the lower end of said reed, means attached to said reed for moving it, said body having an elongated chamber therein, and a relatively heavy liquid partially illing said chamber and arranged to gravitate toward one end of said chamber opposite to the direction of movement of said reed each time said reed moves from the vertical position thereof toward its extreme positions, whereby said liquid during its movement is effective to control the amplitude of swinging movement of said pendulum on both sides of -its vertical axis.

25. In a relay, the combination comprising, a generally square cut body having a horizontally extending upper surface and having a screw-threaded hole therein extending substantially parallel to said upper surface, a reed having a relatively long dimension disposed in a vertical position, said reed being pivotally mounted at its upper end for oscillation and at its lower end secured to said body, means connected with said reed for oscillating it, a weight for controlling the amplitude of said reed fitted on the upper surface of said body in such manner to besupported in upright position thereon, said Weight including two parallel legs spaced from each other and integrally joined at their one ends to form a slotted hole, said legs of said weight straddling the screw-threaded hole in said body, and a screw for detachably securing said weight to said body entering said slotted hole and thread- 21 ing into said screw-threaded hole suiciently to frictionally clamp said weight to said body,`said slotted hole in saidweight enabling said weight to be slipped from `said screw in endwise fashion when itis desired just by slightly unloosening said screw.

26. In a timing relay including 'means for closing a timing contact after the expiration of a predetermined time interval following the initial energization of 'said relay, the combination comprising, an electromagnet and an armature cooperating with said electromagnet and movable relative thereto between a biased nonattracted position kand an attracted position in response to the energization of said electromagnet, a pendulum operatively connected withr said armature movable between two extremities of oscillation in response to energy imparted thereto by movement of sa-id armature, a generally square cut body secured to said pendulum at a point removed from the axis of rotation of said pendulum, said body 'having therein afscrew-threaded hole extending `longitudinally in a plane generally perpendicular to the vertical axis of said pendulum, a weight yloosely iitted on the upper side of'said body so as to be supported in upright position by Vsaid body, said Weight having a pair of rigid parallel legs spaced from each other and joined at their one ends such to form a slot in said weight, and la. 'screwpassing through the slot in said weight adjustably threading into said screw-threaded hole an amount to draw said legs tightly against said body to thereby removably and frictionally lock said weight to said body.

27. In a timing relay including a timing contact, an operating ladder adapted to be moved into engagement with said contact for actuating it after `a `predetermined time interval following the initial energizat-ion of said relay, and time interval adjusting apparatus for controlling the time interval of said relay, saidapparatus comprising, a pinion mounted on an axis for rotation about said axis, a rack bar meshing with said pinion for rotating it, manually adjustable screw means directly cooperative with said rack bar for variably positioning said rack bar in different forward and backward relation to said pinion for effecting clockwise and counterclockwise rotation of said pinion,

and an actuating member secured to said ,pinion engageable with said operating ladder when and only when said pinion rotates a predetermined angular extent, the parts being proportioned such that the position of said actuating member relative to said operating ladder varies directly in accordance with the direction and extent of the angular movement of said pinion when said screw is adjusted.

n 28. ln a timing relay including a timing contact, an operating ladder adapted to be moved into engagement with said contact for actuating it after a predetermined time interval following the initial energization of said relay, and time interval adjusting apparatus for controlling the time interval of said relay, said apparatus comprising, a fixed bracket, a transverse bolt secured at one end to said bracket and disposed in horizontal position, a pinion rotatably mounted on the other end -of said bolt, a rack bar meshing with said pinion, manually adjustable means for moving said rack bar linearly a variable extent for effecting angular movement of said pinion on said bolt a proportional extent when said means is adjusted, and yactuating means on said pinion engageable with said operating ladder and spaced normally from said operating ladder by a distance corresponding to the present time interval of said relay, whereby each time said rack bar is adjusted said actuating means is repositioned relative to said operating ladder to thereby vary said time interval.

29. In a timing relay of the type having a planetary gear assembly rotatable between a first angular position and a second angular position in response to the energization of said relay, the combination of a segment operatively connected with said planetary gear assembly so as to rotate therewith, a rotatable gear closely spaced from said segment and located in a plane substantially below said segment, a rack bar interposed between said gear and the underside of said segment and meshingwith said gear, manually adjustable means threadably engaged with said segment and directly cooperative with said lrack bar rfor at times moving said rack bar vrelative to said segment to in turn rotate said gear, said adjustable means by means of its engagement'with said segment alsoproviding an operating connection between said planetary gear assembly and lsaid rack bar for causing said rack bar to rotate in synchronism with said planetary gear assembly at other times when said relay becomes energized, a timing contact, an operating ladder movable relative to said contact between a iirst position normally spaced `from said contact to a second position in engagement with said contact vfor actuating it, vand actuating means on said gear effective 'for moving said operating ladder from its first to its second position in response to the rotation of said gear when said relay yis energized.` p

30. `In a timing reley including a frame member for enclosing the parts of the relay, a timing contact, and time interval adjusting apparatus, said apparatus comprising, in combination, a rotatable pinion, a rack bar meshing with said pinion for rotating it, a screw directly cooperativek with said rack bar for variably positioning said rack bar in diiteren't forward and backward relations to said pinion to elect clockwise and counterclockwise rotation of said pinion, actuating means on said pinion eiective for actuating saidtiming contact in response to` a predetermined amount of angular movement of said pinion, said frame member provided with an opening aligned with the longitudinal axis of said screw, an axially movable and rotatable screwdriver tool for adjusting said screw slidably mounted in snug relation in the opening in said frame member, said screw provided at one end adjacent to said tool with a rectangular slot which vis just Wide enough to receive the tip end of said tool when said tool is moved into engagement with said screw, and biasing means for biasing said tool away from said screw so that the other end of said tool automatically seals said hole against the entrance of foreign matter at times when said screw is knot being adjusted.

3l. In a relay having at least two electrically conductive contact springs, an actuable operating ladder operatively connected with one of said contact springs for moving it relative to the other one of said contact springs at times when said ladder is actuated, agenerally elongated andlongitudinally extending supporting spring lixed atone end and disposed alongside said operating ladder at its free end, a projection on said ladder in a plane substantially normal to the longitudinal axis of said supporting spring, the free end'of said supporting spring engaging the underside of saidr projection and constituting an upwardly ybent portion extending partially around and engaging the upper side of said segment an extent sutiicient to restrict movement of said ladder upwardly away from said supporting spring, and movement outwardly away from and parallel to the longitudinal axis of said support- .ing spring, and means on said projection cooperating with said supporting spring when said operating ladder is mounted in position vfor preventing said ladder from being displaced from said supporting spring in a direction toward the xed end ofk said supporting spring.

32. In arelay having at least two electrically conductive contact springs, an actuable operating ladder operatively connected with one of said contact springs and operable for moving it relative tothe other contact spring when said ladder is actuated, a generally elongated supporting spring 'xedat oneend and extending longitudinally in a predetermined direction to a point alongside said ladder at its free end, a generally U-shaped projection on said ladder arranged with the bight of the U substantially normal to the longitudinal axis of said supporting spring and with the legs of said projection extending in said predetermined direction, said legs of said projection disposed above said supporting spring coplanar with each other and 23 parallel to said supporting spring, the free end of said supporting spring engaging the underside of said projection in supporting relationship and constituting an upwardly bent portion entering between the legs of said projection and terminating in a pair of oppositely disposed flange portions, each of said ange portions on the extreme end of said supporting spring overlying one of the legs of said projection, the parts being proportioned such that to de tach said ladder from said supporting spr-ing it is necessary only to forcibly completely displace each of the flange portions on said supporting spring away from their posi tions above the legs of said projection.

33. A timing relay comprising, in combination, a ro tatable shaft provided at one end With a ratchet wheel for at times rotating said shaft in steps, said shaft provided j at its other end with a gear, a clutch assembly including a second gear concentric with said shaft spaced from and alongside said rst gear, braking means for at times ren-- dering said second gear immovable, a planetary gear assembly cooperating with said first and second gears in such manner that when said second gear is immobilized and said shaft is being stepped it travels angularly about thel axis of said shaft, a pair of contact fingers one movable'y relative to the other, an actuable operating ladder adapted to move the movable contact finger relative to the other' contact finger when said ladder is so actuated, means intermediate said operating ladder and said planetary gear assembly and operatively connected with said planetary gear assembly and normally spaced from said operating ladder for actuating said ladder when and only when said planetary gear assembly has traveled a predetermined angular distance about the axis of said shaft, and means for controlling the initial spacing between said operating, ladder and said actuating means.

34, A timing relay comprising a core having -a winding thereon, said core further having an aperture therethrough. extending longitudinally in alignment with its axis from end to end, a first pole piece projecting :from one end of said core and provided with an aperture aligned axially with the aperture in said core, a bushing mounted in the aperture in said core and projecting outwardly from the other end of said core, a second pole piece rotatably mounted on the projecting portion of said bushing and provided on the side opposite to said core with a iirst gear, means effective when and only when said winding is energized for engaging said pole pieces for immobilizing said second pole piece with respect to said Core, a shaft mounted in said bushing rotatable relative to said core and extending axially beyond said first pole piece and said first gear, a second gear on the end of said shaft adjacent to said first gear, said shaft provided at its other end with pawl and ratchet means effective for at times rotating said shaft in steps, an actuable operating ladder, a first contact finger and a second contact finger adapted to be moved by said operating ladder into engagement with said first contact finger when said operating ladder is so actuated, a planetary gear assembly cooperating with said first and second gears in such manner that when said Winding is energized and said shaft is being stepped said planetary gear assembly travels angularly about the axis of said shaft, actuating means responsive to said angular movement of said planetary gear assembly effective when and only when said planetary gear assembly has traveled a predetermined distance for actuating said operating ladder, and means for adjusting the initial position of said actuating means with respect to said operating ladder for varying the distance said planetary gear assembly must travel before said operating ladder is so actuated.

35. A timing relay comprising a core having a Winding thereon, said core further having an aperture therethrough extending longitudinally in alignment with its axis from -end to end, a bushing mounted in the aperture in said core and provided with a portion projecting outwardly Lfrom one end of said core, a pole piece spaced from said yone end of said core by a suitable air gap rotatably mounted on the projecting portion of said bushing, a first Agear on said pole piece on its side opposite to said core, :means effective when and only when said winding is energized for engaging said pole piece for preventing it from Arotating with respect to said core, a shaft rotatable in .said bushing relative to said core projecting axially be- `yond said first gear and the other end of said core, a second gear on said shaft on the end thereof adjacent to said Lfirst gear, means operatively connected with the other end `of said shaft for at times rotating said sht in steps, an ,actuable operating ladder, a pair of contact fingers, one of said contact fingers movable relative to the other one .and adapted to be moved by said operating ladder into .engagement 4with said other contact finger when said ladder is so actuated, a planetary gear assembly adapted to 4cooperate with said first and second gears in such manner that when said Winding is energized and said shaft is Ibeing stepped said planetary gear assembly travels angudarly about the axis of said shaft, a fixed bolt concentric with said shaft located with its one end closely adjacent to said second gear, a third gea-r rotatable on said bolt, .a rack bar meshing `with said third gear, a segment con- :necting With said planetary gear assembly and with said rack bar such that said rack bar and said third gear are rotated in response to angular movement of said planetary gear assembly, an adjustable screw threadably engaging said segment and connecting with said rack bar so as to enable said rack bar to be moved linearly when said screw -is adjusted to at times rotate said third gear independently of said planetary gear assembly, said segment provided with an index, an actuating member secured -to said third gear engageable with said operating ladder for actuating it when and only when said planetary gear assembly has traveled a predetermined distance about the axis of said shaft, whereby each time said screw is adjusted the initial position of said actuating member with respect to said operating ladder varies to correspondingly establish a different operating time interval for said relay, and a scale secured to said actuating member to cooperate with said index 'for indicating the time interval of said relay.

References Cited in the file of this patent UNITED STATES PATENTS 176,309 Hile Apr. 18, 1876 1,255,552 Nachod Feb. 5, 1918 1,483,876 Goff Feb. 19, 1924 1,537,796 Bossard et al. May 12, 1925 1,614,953 Goff Jan. 18, 1927 2,198,704 Lazich Apr. 30, 1940 2,268,235 Aamodt Dec. 30, 1941 2,311,637 Buchanan Feb. 23, 1943 2,320,310 Stoddard et al May 25, 1943 2,395,905 'Oetzel Mar. 5, 1946 2,705,058 Harter Mar. 29, 1955 2,739,485 Sengebusch Mar. 27, 1956 2,751,461 Nicolaus `Tune 19, 1956 2,762,866 Sengebusch Sept. 11, 1956 2,830,139 Wells Apr. 8, 1958 2,847,534 Edgarton Aug. 12, 1958 2,916,582 Hufnagel Dec. 8, 1959 

1. AN ELECTROMAGNETIC CLUTCH ASSEMBLY COMPRISING A STATIONARY CORE HAVING A WINDING MOUNTED THEREON, A FIRST POLE PIECE PROJECTING FROM ONE END OF SAID CORE, A SECOND POLE PIECE AT THE OTHER END OF SAID CORE MOUNTED FOR ROTATION ABOUT THE LONGITUDINAL AXIS OF SAID CORE, AND MEANS NORMALLY BIASED APART FROM SAID FIRST AND SECOND POLE PIECES AND MOVABLE INTO ENGAGEMENT WITH SAID POLE PIECES TO PREVENT SAID SECOND POLE PIECE FROM ROTATING WITH RESPECT TO SAID FIRST POLE PIECE WHEN SAID WINDING BECOMES ENERGIZED. 